FCC Measurement Uncertainty & Calibration 2

Question 1

What is the typical calibration interval for antennas used in FCC radiated emissions testing?

Accepted Answer

Annually (every 12 months) unless use or damage warrants more frequent calibration

Answer

Most accreditation bodies and laboratory best practices require antenna calibration on an annual basis, with additional calibration required if the antenna is dropped, repaired, or shows signs of damage.

Question 2

What is 'antenna factor' (AF) and how is it used in radiated emissions measurements?

Accepted Answer

A calibration factor that converts the voltage at the antenna terminal to the incident electric field strength at the antenna

Answer

Antenna factor (dB/m) is added to the measured receiver voltage (dBμV) to obtain the electric field strength (dBμV/m): E = V + AF, and it accounts for the antenna's frequency-dependent sensitivity.

Question 3

What is the purpose of an 'uncertainty budget' in a laboratory's test report?

Accepted Answer

To document all identified uncertainty sources, their magnitudes, and their combined contribution to the total measurement uncertainty

Answer

An uncertainty budget is a structured table that identifies each source of measurement uncertainty, quantifies its contribution, and combines them (using root-sum-of-squares for uncorrelated components) to give the total combined uncertainty.

Question 4

What does ISO/IEC 17025 require regarding equipment used for testing and calibration?

Accepted Answer

All equipment must be calibrated and have calibration records maintained, with calibration traceable to SI units

Answer

ISO/IEC 17025 clause 6.4 requires that laboratories maintain and calibrate all equipment that has a significant effect on the validity of results, with records demonstrating traceability to SI units.

Question 5

What is 'measurement repeatability' in the context of EMC testing?

Accepted Answer

The closeness of agreement between successive measurements of the same measurand under the same conditions

Answer

Repeatability refers to measurement results obtained by one operator, with one instrument, in one location, over a short time period, showing how consistent the measurement process is under unchanged conditions.

FCC - Federal Communications Commission Certified Laboratory Practice Test

FCC - Federal Communications Commission Certified Laboratory Practice Test

FCC Measurement Uncertainty & Calibration 2